Technical FAQ: Installing Campagnolo cassettes

When a Campy cog is incorrectly installed on a Zipp freehub body, as this one is, none of the three wider, symmetrical tabs of the cog engage a rail, so they offer no support against pedaling forces. (The tab’s leading edge, encircled in red, is not resting against anything.) Without the stress distributed over the four tabs that are meant to engage the freehub body, the single, narrow tab can become overloaded, breaking the cog. Photo courtesy Dan Large of Campagnolo USA